This invention relates to polariser arrangements and more particularly, but not exclusively, to arrangements which are suitable for the reception of both linearly and circularly polarised waves.
In a receiving system, for example for receiving a signal from a satellite, after the signal has been received at a dish reflector, it is transmitted along a waveguide to a detector. A polariser is included in the waveguide between the receiving dish and the detector to ensure that only signals with the correct polarisation are transmitted along the waveguide.
In one type of polariser, a ferrite rod is located in the waveguide and is surrounded by a bias coil around the waveguide. It acts as a linear polariser to transmit either vertically or horizontally polarised waves, the mode of polarisation selected being controlled by applying current of an appropriate magnitude and polarity to the bias coil.
The present invention arose from an attempt to provide a compact polariser arrangement which may be fabricated at low cost and which is particularly suitable for use with equipment for receiving satellite signals.